Conventionally, heat radiation systems employing heat sinks, heat pipes, thermosyphons and the like have been known as heat radiation systems radiating heat generated at heat sources. For a heat radiation system with a heat sink attached to a heat source, the heat sink has a significant distribution in temperature. As such, the remoter it is from the heat source, the less it contributes to heat radiation. It thus has its limit in improving heat radiation performance. In contrast, heat radiation systems employing a heat pipe, a thermosyphon or the like employ a working fluid to transfer heat generated at a heat source. As such, they have a significantly higher ability to transfer heat than a heat sink and can thus maintain high heat radiation performance.
A heat pipe is a capillarity driven heat transfer device circulating a working fluid through a capillary action of a wick arranged in a closed circuit. By contrast, a thermosyphon is a gravity driven heat transfer device utilizing a difference in density of a working fluid that is caused as the working fluid evaporates and condenses. Note that a loop thermosyphon is a thermosyphon configured to circulate a working fluid in a closed circuit formed in a loop.
A loop thermosyphon equipped Stirling refrigerator is disclosed for example in Japanese Patent Laying-Open Nos. 2003-50073 (Patent Document 1) and 2001-33139 (Patent Document 2).
Patent Document 1 discloses a system that exchanges heat of a heat radiating portion (or a heated portion) of a Stirling refrigerating machine (hereinafter also referred to as “conventionally example 1”). The system includes an evaporator and a condenser associated with the heated portion and piped and thus connected together. The condenser is positioned to be higher than the evaporator and water, hydrocarbon or a similar natural coolant is sealed to thermosyphonally transfer and radiate heat.
When the Stirling refrigerating machine starts to operate, the heat radiating portion is increased in temperature and in the evaporator a heat transfer medium is heated and thus evaporates, and flows through a pipe into the condenser. Simultaneously, as a heat radiation fan rotates, the air external to the refrigerator is introduced through a suction port into an air duct. The air passes between a fin of the condenser and is then blown out of the refrigerator through an outlet port, when the heat transfer medium is cooled and thus condensed in the condenser. The condensed heat transfer medium passes through a pipe and thus flows down to return to the evaporator. The heat transfer medium is thus naturally circulated and the Stirling refrigerating machine's heated portion has its heat radiated external to the refrigerator.
Patent Document 1: Japanese Patent Laying-Open No. 2003-50073
Patent Document 2: Japanese Patent Laying-Open No. 2001-33139